Pick resistant lock cylinder



July 24, 1962 N. A. WELCH ETAL 3,045,468

PICK RESISTANT LOCK CYLINDER Filed April e, 1960 J J J D INVENTORS/V/c//oLHs H. Ww. cH

13g/mines /fz/wvgr/fPaBz'Pn PICK RESISTANT LCK CYLINDER Nicholas A.Welch, West Hartford, Conn., and Charles Kenneth Roberts, East Canton,Ohio, assignors, by mesne assignments, to Charles K. Roberts, Baltimore,

Filed Apr. 6, 1960, ser. No. 20,443 3 claims. (ci. '1o- 421) Thisinvention relates to a lock `cylinder and more particularly to a lockcylinder of the pin tumblervtype which is especiallyr adapted to resistpicking.

The present invention provides a pin tumbler lock cylinder which isespecially well suited for use in locking devices such as padlocks, doorlocks, drawer locks, cabinet locks and the like where a' high degree ofsecurity is required. While most `such locking devices may be defeatedby actually destroying the lock mechanism or physically altering thelock cylinder as by drilling or the like, such methods are likely toattract immediate attention as they are being carried out and are, inany event, thereafter easily detected. Picking techniques, on the otherhand, leave no telltale evidence that the lock has been tampered with,but are usually thwarted if success cannot be quickly achieved. lIt istherefore apparent that the degree of pick resistance inherent in a lockcylinder is of singular importance.

Most pin tumbler lock cylinders hereto-fore devised can be successfullypicked in a relatively short time and hence do not afford a very highdegree of security. Of

. course, lock cylinders have been made which were difcult to pick, butthese generally involved complicated mechanisms, odd shaped keyways andkeys, compound tumbler sets or other such unusual structure, and were soexpensive to manufacture that they were rarely commercially successful.

The present invention therefore has as its primary object the provisionof a pin tumbler lock cylinder which is extremely diicult, if notimpossible, to pick, is comparatively inexpensive to manufacture and isyet reliable in action so that it may be easily operated by the properkey.

A further object of this invention is to provide a lock cylinder 'whichis highly pick resistant and yet does not involve the use of complicatedand expensive structure.

Another object of the present invention is to provide a pin tumbler lockconstruction which may be readily ernbodied in conventional lockingdevices of the type mentioned above .without requiring radical changesin the structure of the locking devices.

As is well known to those skilled in the lockart,

'Y conventional techniques for picking pin tumbler lock cylindersrequire the application of torque to the key plug of the lock cylinderto effect fractional turning movement thereof while the pin tumblers aremanipulated to bring them into unlocking or shear position. In onemethod, commonly known as up picking, torque is applied to the key plugand the pin tumblers are then successively raised against their springswit-h a picking tool inserted into the keyway until all of the tumblershave been moved into shear position. The reverse of this method, knownas down picking, involves simultaneously raising all of the tumblers asfar as possible and then exerting torque on the key,plug. The tumblersare then permitted to move downwardly under the inlluence of theirrespective tumbler springs while an attempt is made to catch the propertumblers on the exposed edge portions of the tumbler bores in the keyplug to thereby release the key plug for turning movement. In otherpicking methods, the tumblers are Vibrated rapidly up and down with asuitable tool or by striking the locking device -With a mallet whilesimultaneously exerting a flice torque on the key plug in order to trapthe tumblers in locking position.

Pin tumbler lock cylinders may also be picked by skilled persons usingthe well known impression method. This method is essentially a downpicking technique and involves the use of an uncut key blank of theproper cross-sectional shape to it the keyway of the lock cylinder. Thiskey blank is usually provided with a burnished top edge and is insertedinto the keyway to lift all of the pin tumblers above their normal shearpositions. Heavy torque is then applied to the key plug to clamp thepins in position and an up and down, in and out rocking motion isapplied to the key blank to cause the clamped pins to mark lthe edge ofthe key'blank. Thekey blank is then examined and several fine file cutsare made at each mark on the edge of the key blank. This operation isrepeated until the key blank has been cut deeply enought to lower all ofthe pins to shear position.

In order to prevent picking by4 these and other wellknown methods, weprovide a lock cylinder having means therein which prevent the tumblersfrom being properly manipulated when torque is applied during pickv ingoperations and which also serve to bale and confuse for Vlimitedrotation in the body of the lock cylinder,l

the amount of rotation permitted the control member being ineffective tocause operation of the mecha nism of the locking device in which thelock cylinder is contained. The cylinder body, the control member andthe key plug have the usual rows of tumbler bores which are normallyaligned and contain a series of tumbler elements including conventionalpin tumblers. In the normal locking position of said tumblers, thekeyplug 'and the control member are locked together bythe pin tumblers andare adapted to rotate in said cylinder body so that the application of atorque to the key plug, regardless of how slight it may be, will causethe control member to rotate therewith.

In each of the tumbler bores of the control member we provide a uniquecontrol tumbler which is responsive to the torque applied to saidcontrol member to prevent successful manipulation of the pin tumblers.The control tumblers are preferably in the form of balls and are capableof acting in diverse and unpredictable ways to defeat various pickingtechniques as will be hereinafter described.

The basic conce-pt of our invention may be embodied in many physicalforms, and several of these forms are shown by way of example in theaccompanying drawing in which:

FIG. l is an elevational view, partly in central vertical section,illustrating a lock cylinder embodying our invention, said lock cylinderbeing shown in its normal, locked condition.

lFIG. 2 is a sectional end view of the lock cylinder taken on line 2--2of IFIG. l.

IFIG. 3 is a sectional end view illustrating one manner in which uppicking operations are defeated by the control tumblers of ourinvention.

FIG. 4 `is a diagrammatic view further illustrating the principle ofoperation of the control tumblers.

FIG. 5 is a sectional end view illustrating one manner in lwhich downpicking operations are defeated.

FIG. 6 is a view similar to FIG. 1, but illustrating the normaloperation of the lock cylinder of the proper key.

FIG. 7 is a fragmentary sectional end View illustrating a modified formof control tumbler for use in the lock cylinder.

FIG. 8 is a similar view illustrating another type of control tumblerwhich maybe used in the lock cylinder.

The lock cylinder embodying our invention and illustrated in the drawingcomprises a body including a cylinder portion -6 and an integral chamberportion 7 which extends radially from said cylinder portion. Thecylinder portion 6 contains an axial bore which is Open at the inner endof said body and terminates short of its outer end to provide an outerwall `6-a thereon. A longitudinal row of aligned, equally spaced driver`bores 9 extend radially from the bore 8 into the chamber 7 and saidbores are closed at their upper ends by a plate 7-a.

In accordance with the present invention, a control member in the formof a sleeve 10 is rotatably mounted in the bore 8 of the body 5 and thecontrol sleeve contains a row of radially extending tumbler bores 11which are alignable with the driver bores 9 as shown in FIGS. l and 2.

A key plug 12 is mounted to rotate in the control sleeve 10 and extendsthrough a coaxial opening 13 in the outer wall 6-a of the body 5. At itsouter end, said key plug is provided with a flange 1'4 which rotates ina recess 15 in said outer wall and prevents inward axial movement of thekey plug. The inner end of the key -plug has an axial extension 16 ofreduced diameter which projects from the inner end of the control sleeve10 and receives a cap 17. The said cap is secured to the key plugextension 16 by a pin 18 and is provided with an annular flange 19 whichengages the inner end of the control sleeve 10. It will be seen that thecap 17 prevents outward axial movement of the key plug and inward axialmovement of the control sleeve to thereby maintain the lock cylinder inassembled condition. The cap 17 is, in the present illustration,provided -with a stud 20 which is adapted to operate the lock mechanismof the locking device in which the lock cylinder is contained.

The key plug 12 has an axially extending keyway 21 of irregularcross-sectional shape, and it will be noted that said keyway iscontained entirely within the key plug so that it is closed along itsbottom to prevent access to the control sleeve 10 through the keyway.The key plug also contains a row of radially extending pin tumblersbores 22 which communicate with the keyway and are normally aligned withthe tumbler bores 11 and 9 in the control sleeve 10 and the body 5respectively.

Each of the aligned sets of tumbler bores of the lock cylinder slidablycontain a series of tumbler elements of predetermined lengths which arenormally disposed in the positions illustrated in FIG. 1. In the presentembodiment, each series of tumbler elements includes a change pin 23 andan intermediate pin 24 which are slidably disposed in the tumbler bores22 and 11 of the key plug and the control sleeve respectively. Theintermediate pin tumblers 24 normally extend across the shear line 25,defined by the adjacent surfaces of the key plug and the control sleeve,and lock these parts together.

Each series of tumbler elements also includes a novel control tumbler 26which is preferably in the form of a -sphere or ball as shown in IFIGS.1 to 6. The control 'tumblers are normally disposed in the tumbler bores11 in the control sleeve, but project slightly above its peripheralsurface. 'In this position, the upper segment of each sphere extendsacross the shear line 27, defined by the peripheral surface of thecontrol sleeve and the wall of the bore8, and into the aligned tumblerbore 9 in the body 5 as best shown in FIG. 2. The control tumblers 26and the pin tumblers 24 and 23 are yieldingly held in normal lockingposition by driver tumblers 28 which are slidable in the tumbler bores 9of the body 5 and are biased downwardly into engagement with the controltumblers by tumbler springs 29.

hereinafter described, such rotation must be limited to an amount lessthan that required to operate the mechanism of the locking device inwhich the lock cylinder is contained. In order to accomplish this, weprovide a slot 30 in the periphery of the control sleeve and a stop pin31 in the body 5. The stop pin 31 extends into said slot and isengageable by the sidewalls thereof to limit rotation of the controlsleeve to a predetermined num ber of degrees.

It has been found that the degree of pick resistance of lock cylindersconstructed in accordance with the present invention is directlyproportional to the number of control tumblers 26 provided therein.Experimental models with a single series of tumbler elements arranged asshown could easily be picked. When two series of tumbler elements wereprovided, picking became more difficult, but could be accomplished. Lookcylinders with three series of tumbler elements could not besuccessfully picked in the time allotted, and exhaustive tests haveshown that lock cylinders constructed as shown in `FIG. 1 are capable ofresisting indefinitely all presently known picking techniques.

While the spherical control tumblers 26 act in diverse and unpredictableways to prevent proper manipulation of the pin tumblers during pickingoperations, FIGS. 3 and 4 of the drawing illustrate one manner in whichup picking is prevented. As previously mentioned, the tumbler elementsnormally occupy their lowermost positions, as shown in FIGS. 1 to 4,wherein the key plug l2 is locked to the control sleeve 10 by theintermediate pin tumblers 24, and the upper segments of the sphericalcontrol tumblers 26 project into, but are spaced from, the lower edgesof the tumbler bores 9. When torque is applied to the key plug 12, sayin la clockwise direction as shown by the arrow 32 in FIG. 4, both thekey plug and the control sleeve will rotate together and the controltumblers 26 will be carried into engagement with the lower edges of thetumbler 4bores 9. Since the centers of the spherical control tumblersare disposed below the edges of the tumbler bores 9, the surfaces ofsaid control tumblers which engage said edges are disposed angularlythereto and act as cam surfaces which cause said control tumblers to becammed or thrust downwardly, as indicated by the Iarrow 33, to preventthe pin tumblers 23 and 24 from being raised. If the torque isincreased, the downward force exerted by the control tumblers is Ialsoincreased proportionately which makes raising of the pin tumblers thatmuch more diiiicult. Should the upward force exerted on the pin tumblers23 with vthe picking tool `and the torque applied to the key plug be soproportioned as to pennit raising `of one or more series of 'tumblerelements, the control tumblers 26 will cam the control sleeve backtoward its normal position as they are forced upwardly in the tumblerbores 11 and into the tumbler bores 9. As soon as the centers of one ormore of the control tumblers move past the shear line 27, they will becammed upwardly by the left-hand edges of the tumbler bores 11 in thecontrol sleeve which will cause them to pop upwardly into the tumblerbores 9 in the cylinder body, thus permitting the control sleeve to turnslightly before the person attempting to pick the lock has time torealize what has happened. The control tumblers so affected will then betrapped up in the tumbler bores 9, as shown in FIG. 5, and will preventthe force exerted by the tumbler springs 29 from being transmitted tothe pin tumblers 23 and 24. In the absence of such spring pressure thepin tumblers 23 and 24 are free to move up `and down in their bores andit is then impossible to feel their positions with respect tothe shearline 25.

FIG. 5 .also illustrates what may happen when down picking techniquesare employed in an attempt to pick the lock cylinder. In such ya case,all of the tumbler elements are rst raised as far as possible with thepicking tool thus moving the ycontrol tumblers 26 into the tumbler bores9 in the cylinder body. Torque is then applied to the key plug, say inla clockwise direction as shown, but

since the key plug will be locked to the control sleeve by one or moreof the pin tumblers 23, the control sleeve will rotate with the key plugwhen the torque is applied. It will be apparent, therefore, that theedges of the tumbler bores 11 in the control sleeve will then bepositioned as shown in FIG. 5 to engage and prevent the descent of thecontrol tumblers when the upward pressure on the pin tumblers isreleased. Asa result, the tumbler springs are prevented from acting uponthe pin tumblers 23 and 24 so that their positions with respect to theshear line 25 cannot be determined. All in all, the described 4and otherfunctions of the control tumblers 26 serve -to baflle and confuse theperson attempting to pick the lock .and make picking extremely difficultif not impossible.

While the control tumblers 26 provided by our invention effectivelydefeat picking, they cause no interference with the normal operation ofthe lock cylinder. Referring now to FIG. 6, it will be seen that whenthe proper key 34 is inserted into the keyway 21 the tumbler elementsIare lifted to align the abutting ends of the pin tumblers 23 and 24with the shear line 25 whereupon the key plug may be -rotated relativelyto the control sleeve. Rotation of the control sleeve during keyoperation of the lock cylinder may be prevented by providing anintermediate pin tumbler 24 which is long enough to extend into itsrespective tumbler bore 9 to lock thel control sleeve to the cylinderbody.

While the spherical control tumblers 225 provide the maximum pickresistance, other types of tumbler elements may be used in our lockcylinder to defeat picking. FIG. 7, for example, illustrates a modiedcontrol tumbler which is in the form of a pin tumbler 24-1 having aspherical, or spheroidal, upper end por-tion 24J). Preferably, one suchpin tumbler is provided in each of the tumbler bores 11 of the controlsleeve 1li immediately above the pin `tumbler 23. ln the normal lockingpositions of the tumbler elements, the lower portion of each pin tumbler24-a extends across the shear line 25 to lock the key plug |12 and thecontrol sleeve `lil together. The

` upper segment of the spherical end portion 2li-In of each said tumblerprojects slightly above the .peripheral surface of the control sleeve10` and thus extends across the shear line 27 and into the alignedtumbler bore 9 in the cylinder body. The pin tumblers 23 land 24a arenormally yieldingly maintained in locking position by the spring-presseddriver tumblers 23 as previously described.

The control tumblers 24-a function in the same manner as the sphericalcontrol tumblers 25 to defeat up picking, for when the control sleeve isrotated upon the application o-f a picking torque to the key plug theirspherical end portions 2li-b are carried into engagement with the edgesof the tumbler bores 9. This results in the application of a downwardforce on said control tumblers which prevents the pin tumblers 23 `frombeing raised. The ability of the lock cylinder to resist down pickingand other picking techniques may be effectively increased by usingIcontrol tumblers ot the well known spool or mushroom type whose`function will be apparent to .those skilled in the art.

FIG. 8 illustrates a further modificationof our invention wherein thecontrol tumblers are in the form of wafers 35-35 having opposedspherical surfaces 36-36- Preferably, a pair of said wafers are providedin each of the tumbler bores 11 in the control sleeve between theintermediate pin tumbler 24 and the driver tumbler 2b as shown. In thenormal locking position of the tumbler elements, the spheroidal surfacesof the upper wafers 35 project slightly above the peripheral surface ofthe control sleeve il@ and into the aligned tumbler bore 9 in thecylinder body. When the control sleeve is rotated, it will be apparentthat theA upper wafers will engage the edges of the tumbler bores 9whereupon they will be cammed downwardly to prevent manipulation of thepin tumblers 23 and 24. The wafer control tumblers will also act much inthe same way as the balls 25 to prevent down picking as above described.

From the preceding description, it will be apparent to those skilled inthe art that our invention is capable of many other embodiments thanthose shown. For example, the body 5 may be a padlock body or the bodyof a door knob having the bore `9 and the tumbler bores 9 formeddirectly therein. The important features of our invention reside in theother elements described herein and the particular type of lock body inwhich they are used is of little signicance.

We claim:

l. A' pick resistant lock including a lock body having a bore, a tubularcontrol sleeve rotatable in said bore, means limiting the rotation ofsaid control sleeve in said bore, a key plug mounted to rotate in saidcontrol sleeve and having an axial keyway, said key plug, control sleeveand lock body having radial tumbler bores which are alignable andcommunicate with said keyway, a series of tumblers slidable in saidtumbler bores including pin tumblers normally positioned to lock saidkey plug and said control sleeve together and being movable by a keyinserted into said keyway to unlocking position to release said key plugfor free rotation relatively to said.

control sleeve, tumbler control means normally occupying a position inthe tumbler bore in said control sleeve radially outwardly of the pintumblers in said series, said tumbler control means including at leastone lens-shaped wafer having opposed spheroidal surfaces and in thenormal locking position of said tumblers being disposed so that theupper segment of the upper spheroidal surface projects into the tumblerbore in said lock body in spaced vrelation to the edge portiony thereofto permit rotation of said control sleeve when picking pressure isapplied to said key plug in an attempt to pick said tumblers,the'spheroidal surface of said tumbler control means being carried intoengagement .with said edge portion upon rotation of said control sleevethereby preventing movement of said series of tumblers to unlockingposition, said tumbler control means responsive to applied torque ofsaid key plug producing a locking action and `false indications removedfrom the operating shear line which serves to baffle and confoundpicking attempts.

2. The subject matter set forth in claim l wherein said tumbler controlmeans includes at least one substantially spherical shape that may havean irregular surface.

3. The subject matter set forth in claim 1 wherein said tumbler controlmeans and said control sleeve may be-of a plastic or resilient material.

References Cited in the tile of this patent UNITED STATES PATENTS

